A,B=gets.split
l=[A,B].map &:size
r=A.to_i<=>B.to_i
l.uniq[1]||l[0].times.any?{|i|[A[i],B[i]].sort==[?4,?7]&&r=B[i]<=>A[i]}
$><<[0,A,B][r]